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March 2, 2011

Muscle Loss, Fat Gain Associated With Increased Risk of Death

by Tim Horn

HIV-positive individuals experiencing a loss of muscle mass and an increase in abdominal fat may face an increased risk of death, according to new data from the Fat Redistribution and Metabolic Change in HIV Infection (FRAM) study presented Tuesday, March 1, at the 18th Conference on Retroviruses and Opportunistic Infections (CROI) in Boston.

Muscle loss, a hallmark symptom of wasting syndrome, is still a concern for many people living with HIV. Whether it occurs as a result of disease or aging, muscle loss can negatively affect survival if it is bad enough. This observation prompted Rebecca Scherzer, MD, and her colleagues to pose the following question: Does decreased muscle mass, lipoatrophy and/or gains in abdominal fat predict five-year mortality in a cohort of HIV-positive individuals?

To answer this question, Scherzer turned to the FRAM, which enrolled 1,183 HIV-positive men and women between 2000 and 2002. During the initial examinations of these volunteers, whole-body MRI was used to measure regional and total muscle and fat tissue. Five years later, 794 patients were known to be alive, 128 were known to be dead and the statuses of 261 were unknown.

Using these data, Scherzer’s group looked for associations between muscle/fat measurements—divided into three groups, or tertiles, with the worse muscle measurements in lowest tertile and the worst fat measurements in the highest tertile—and death rates (from any cause) over five years of follow-up.

Deaths from any cause were more likely to occur among those in the lowest muscle measurement tertiles compared with those in the higher tertiles. For example, HIV-positive participants with arm muscle in the lowest tertile had a five-year death rate of 23 percent, compared with 11 percent and 8 percent of those in the middle and highest tertiles, respectively.

After adjusting the data for factors that can potentially skew the results—such as demographics, cardiovascular risk factors, HIV-related factors, inflammatory markers and kidney disease—Scherzer’s group found that lower arm muscle, lower leg muscle and higher amounts of deep belly fat were each associated with an increased risk of death during the five-year follow-up period.

Those in the lowest arm or leg muscle measurement tertiles were twice as likely to die, compared with those in the highest arm and leg muscle measurement tertiles. Similarly, those in the highest tertile of abdominal fat measurements were more than twice as likely to die, compared with those in the lowest fat measurement tertile.

Lipoatrophy—fat loss in the arms or legs—did not appear to be associated with an increased risk of death.

Discussing the clinical implications of these findings, Scherzer noted that Body Mass Index (BMI) measurements—a basic calculation of body fat using a person’s weight and height—may not accurately predict health risks in HIV-positive patients, given that the number will remain constant as muscle mass decreases and fat mass increases. “In turn,” she noted, “clinicians should consider measuring waist circumference and mid-arm muscle circumference in HIV-positive patients, and should be aware that patients with excess central fat may not necessarily have low enough BMI to alert them to their true level of risk.”

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